The field relates to a process for the treatment of crude oils and, more particularly, to the hydroconversion of heavy hydrocarbons in the presence of catalysts to provide useable products and further prepare feedstock for further refining.
As the reserves of conventional crude oils decline, heavy oils must be upgraded to meet world demand for transportation fuel. In heavy oil upgrading, heavier materials are converted to lighter fractions and most of the sulfur, nitrogen and metals must be removed. Heavy oils contain a large proportion of material boiling above 524° C. (or 975° F.) or higher. These heavy hydrocarbon feedstocks may be characterized by low reactivity in visbreaking, high coking tendency, poor susceptibility to hydrocracking and difficulties in distillation. Most residual oil feedstocks which are to be upgraded contain some level of asphaltenes which are typically understood to be high molecular weight compounds that are insoluble in heptane but soluble in toluene as determined by ASTM D3279 or ASTM D6560. A slurry hydrocracking (SHC) process has been found to provide high liquid yields with much reduced coke formation through the use of catalyst particles.
In SHC, a three-phase mixture of heavy liquid oil feed cracks in the presence of gaseous hydrogen over solid catalyst to produce lighter products under pressure at elevated temperature. Iron sulfate monohydrate (ISM) is a conventional SHC catalyst. ISM is sulfided in the reactor to the active phase, pyrrhotite.
Bauxite and laterite have been disclosed as effective SHC catalysts. These naturally occurring minerals may be ground down to smaller size for better dispersion and facilitation of mass transfer. The iron contained in the bauxite or laterite is an effective SHC catalyst when in sulfide form as pyrrhotite.
Toluene can be used as a solvent to dissolve and separate carbonaceous solids from lighter hydrocarbons in the SHC product. The solids not dissolved by toluene include catalyst and toluene insoluble organic residue (TIOR). TIOR includes coke and mesophase and is heavier and less soluble than asphaltenes. Mesophase formation is a critical reaction constraint in slurry hydrocracking reactions. Mesophase is a semi-crystalline carbonaceous material defined as round, anisotropic particles present in pitch boiling above 524° C. The presence of mesophase can serve as a warning that operating conditions are too severe in an SHC reactor and that coke formation is likely to occur under prevailing conditions.
As the number and volume of SHC operations to upgrade heavy oil increase, greater supplies of effective SHC catalyst will become necessary. Since ISM is continuously added to the process and lost in the unconverted pitch, there is a need for more active catalyst materials which can be added at lower concentrations while delivering comparable hydrogenation and mesophase suppression compared to ISM.